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Page 2 of 34 Ma et al. Soft Sci 2024;4:26 https://dx.doi.org/10.20517/ss.2024.20

INTRODUCTION
As the human’s largest organ, the skin provides abundant physiological information for health
[1,2]
management . For instance, skin mechanical deformations reflect health status, including cardiovascular
health , expressions , and joint movements , and sweat at the skin interface contains a series of
[5,6]
[7,8]
[3,4]
[10]
biochemical biomarkers, including lactate , cortisol , etc. Accurate and real-time monitoring of these
[9]
indicators provides users and doctors with important information for precise healthcare [11-13] . Most existing
clinical devices for detecting these indicators exhibit shortcomings, such as high cost, large volume, low
comfort, discontinuous monitoring, etc. Various soft skin electronics have been developed to address these
challenges, characterized by cost-effectiveness, small size, high comfort, and continuous detection
capabilities. These devices have been fabricated using diverse techniques [14,15] , including traditional
lithography and printing technology [17,18] . However, complicated processing, expensive platforms, and
[16]
clean-room environments are required to fabricate most of these soft skin electronics, which increase the
economic cost and hinder the widespread applications of intelligent healthcare.

The laser engraving strategy showcases overpowering manufacturing advantages in effective cost due to
one-step processing and clean-room-free, as well as performance superiority in uniformity and repeatability
originating from precise programmable features. There are various soft skin electronics fabricated by laser
techniques, including laser sintering of metal nanomaterials , laser processing of conductive polymers ,
[19]
[20]
and laser producing of functional materials . Polyimides (PI) are widely utilized in flexible electronics,
[21]
profiting from their remarkable physicochemical properties, such as high mechanical strength and thermal
and chemical stability . Laser engraving with a PI sheet can produce porous graphene, termed laser-
[22]
induced-graphene (LIG) . Laser processing parameters, including laser powers, speeds, and pulse density,
[23]
can regulate the morphology of LIG. The fabricated LIG exhibits excellent conductivity (square resistance <
[23]
10 Ω) [24,25] and a large superficial area of 340 m /g . The overall pattern of LIG can be precisely programmed
2
using computer design. In addition, this processing method is green because it can be finished in ambient
conditions with negligible waste generated. All these advantages inspire researchers to fabricate various
LIG-based flexible devices for broad applications, including soft sensors [26-28] , RF (radio frequency)
circuits , functional surfaces , energy storage , soft robotics , etc.
[29]
[30]
[31]
[32]
This review mainly discussed the recent advances in LIG-based soft skin electronics (LIGS E) for human
2
health management, emphasizing engineering design strategies and intelligent applications. Based on the
[33]
preferred reporting items for systematic reviews and meta-analyses (PRISMA) process , this study mainly
summarized and reviewed the literature from January 2014 to January 2024. Following a rigorous screening
process, a total of 86 articles were thoroughly assessed and subsequently included in this comprehensive
review. As illustrated in Figure 1 [3,26,34-50] , the preparation strategies and the regulatory approaches of LIG for
soft skin electronics are reviewed first. Following this, various applications of LIGS E for intelligent
2
healthcare are reviewed, including biosensors (biophysical and biochemical sensors) and bio-actuators,
power supply, multimodal sensing realization, and artificial intelligence integration. Finally, the potential
challenges and futural outlook of LIGS E for intelligent healthcare are discussed.
2
SYNTHESIS AND REGULATION STRATEGIES OF LIG
Fabrication and properties of LIG
In 2014, Lin et al. discovered accidentally that a commercial CO infrared (IR) laser (wavelength: 10.6 μm)
2
could transform PI film into porous graphene in ambient conditions . As shown in Figure 2A, the
[23]
localized high temperatures induced by the instant laser irradiation can rearrange carbon atoms to porous
LIG structures by breaking C–O, C=O, and N–C bonds. The patterns of LIG can be precisely regulated by
the programmable computer design without using a mask. Benefiting from the thermal effect, the LIG